Design Of Monolithic CC/CV SMPS For Li-ion Battery Charger

Li-ion battery has been widely used as the mainly power for portable devices. To give full play to its own storage characteristics, it also proposes higher requirements for the charging equipment. Therefore, it has been an important project to design a charger which is safe, full charge, quick, small and light.Taking the project "Research on the Series of Power Management ICs" as the background, this paper has described the design of the XD1616, based on the principles of flyback CC(Constant Current)/CV(Constant Voltage) SMPS(Switch Mode Power Supply) and the theory related. This monolithic device applied to Li-ion charger is a CC/CV SMPS with safe characteristic, high efficiency and novel control strategy.XD1616is used in the flyback topology, so the Input and output are fully isolated, it improves the charging safety. The IC, using a PSM(Pulse Skipping Modulation) control mode instead of the traditional PWM(Pulse Width Modulation), has a much higher efficiency. The state machine which is novel and intelligent is the core module, besides the digital control method has no problem of loop stability occurs in the traditional analog design. The chip has frequency jittering function which can solve the problem of EMI and reduce the size and cost of the charger by lower the requirements for the component of EMI(Electromagnetic Interference) filter circuit. This device has a precision complex-compensated current reference based on currents difference mode which keep the oscillator generate a stable frequency by providing a constant current. XD1616integrates a high voltage charging circuit to simplify the external application circuit and reduce the charger size. The chip also has a cable drop compensation function which makes the CV more accurate and full charge.The optimization and simulation of XD1616were completed by using Cadence software based on the0.5um BCD(Bipolar-CMOS-DMOS) process, then taped out. The test results for the IC show that:in the case of light load, the CV output is4.76-4.86V, and in the case of heavy load, the CC output is almost1A, both of them meet the tolerance. Therefore the function and performance of the chip can meet the design requirements.